| Title: |
Investigating the influence of radio-faint AGN activity on the infrared-radio correlation of massive galaxies |
| Authors: |
Peluso, Giorgia; Delvecchio, Ivan; Radcliffe, Jack; Daddi, Emanuele; Deane, Roger; Jarvis, Matt; Zamorani, Giovanni; Prandoni, Isabella; Gitti, Myriam; Spingola, Cristiana; Ubertosi, Francesco; Sargent, Mark; Smolcic, Vernesa; Wang, Wuji; Delhaize, Jacinta; Jin, Shuowen; Deller, Adam |
| Publication Year: |
2025 |
| Subject Terms: |
Astrophysics of Galaxies |
| Description: |
It is well-known that star-forming galaxies (SFGs) exhibit a tight correlation between their radio and infrared emissions, commonly referred to as the infrared-radio correlation (IRRC). Recent empirical studies have reported a dependence of the IRRC on the galaxy stellar mass, in which more massive galaxies tend to show lower infrared-to-radio ratios (qIR) with respect to less massive galaxies. One possible, yet unexplored, explanation is a residual contamination of the radio emission from active galactic nuclei (AGN), not captured through "radio-excess" diagnostics. To investigate this hypothesis, we aim to statistically quantify the contribution of AGN emission to the radio luminosities of SFGs located within the scatter of the IRRC. Our VLBA program "AGN-sCAN" has targeted 500 galaxies that follow the qIR distribution of the IRRC, i.e., with no prior evidence for radio-excess AGN emission based on low-resolution (~ arcsec) VLA radio imaging. Our VLBA 1.4 GHz observations reach a 5-sigma sensitivity limit of 25 microJy/beam, corresponding to a radio brightness temperature of Tb ~ 10^5 K. This classification serves as a robust AGN diagnostic, regardless of the host galaxy's star formation rate. We detect four VLBA sources in the deepest regions, which are also the faintest VLBI-detected AGN in SFGs to date. The effective AGN detection rate is 9%, when considering a control sample matched in mass and sensitivity, which is in good agreement with the extrapolation of previous radio AGN number counts. Despite the non-negligible AGN flux contamination (~ 30%) in our individual VLBA detections, we find that the peak of the qIR distribution is completely unaffected by this correction. We conclude that residual AGN contamination from non-radio-excess AGN is unlikely to be the primary driver of the M* - dependent IRRC.; 10 Pages, 6 Figures, 1 Table. Accepted for publication in A&A |
| Document Type: |
Working Paper |
| Access URL: |
http://arxiv.org/abs/2509.17536 |
| Accession Number: |
edsarx.2509.17536 |
| Database: |
arXiv |